Sarcopenia is a prevalent condition in older populations characterized by age-related loss of muscle mass and function, leading to a number of negative health impacts . Evidence shows that sarcopenia is related to higher risks of functional decline, disability, falls, incidence of hospitalizations, and mortality . Moreover, patients with sarcopenia are reported to have higher healthcare costs than those without sarcopenia, and this contributes to greater economic burden to the healthcare systems in society . It is estimated that in older community-dwelling Taiwanese, the prevalence of sarcopenia and severe sarcopenia is 7.1% and 5.6%, respectively . Another study using Sluggishness, Assistance in walking, Rise from a chair, Climb stairs, Falls (SARC-F) questionnaire (a 5-item screening tool for sarcopenia) to assess sarcopenia showed that the prevalence of sarcopenia was 6.1% in older adults . With the rapid increase of older population in Asia , there is a need to further identify the factors associated with sarcopenia to develop strategies to prevent or delay the condition in older adults.
From the socio-ecological models, a person’s health condition can be viewed as an interaction between an individual’s behavior and his/her surrounding environment . Among the different dimensions of environment, the built environment (a human-constructed physical aspects) plays an important role on public’s health . Notably, neighborhood-built environment, where people live their everyday lives, is considered as a foundation of health and well-being [9, 10]. This environment is particularly critical to older population because older adults may face functional decline and narrowed social networks, as they tend to spend more time in their own neighborhoods . In this context, it is critical how a neighborhood-built environment can provide opportunities such as infrastructure, shops, destinations, and transportation (known as walkability) for older adults to be physically active  and have healthy dietary behavior . Therefore, it is possible that walkable environments with favorable destinations can play a protective role to older adults’ risks of sarcopenia because a high-walkable neighborhood environment can provide more opportunities for older adults to access healthy food and engage in active daily lifestyle.
A growing body of research states that there is a connection between neighborhood walkability and older adults’ geriatric syndrome such as weight status [13–15], cognition , depression , physical function , and functional disability . However, it remains unclear how neighborhood walkability may relate to risks of sarcopenia in older adult population. To inform the policy of Healthy Aging or Aging in Place, there is an urgent need to further provide evidence-based information on the relationship between neighborhood walkability and risks of sarcopenia. A review reports that neighborhood walkability (determined by walk score) is positively related to physical activity and negatively associated with risks of obesity, cardiovascular disease, and cancer in Western countries  but not associated with recommended levels of physical activity but positively related to prolonged sedentary time in Taiwan . It is possible that the associations between neighborhood walkability and health outcomes may differ in different contexts. Moreover, with recent studies suggesting that there may be no linear association between neighborhood walkability and health behavior  or health outcomes , we hypothesized that there may be a nonlinear association between neighborhood walkability and risks of sarcopenia in Asian context. Thus, this study aimed to examine whether neighborhood walkability is nonlinearly associated with risks of sarcopenia in a sample of older Taiwanese adults.